ABSTRACT
[Fe(tvp)2 (NCS)2 ] (1) (tvp=trans-(4,4'-vinylenedipyridine)) consists of two independent perpendicular stacks of mutually interpenetrated two-dimensional grids. This uncommon supramolecular conformation defines square-sectional nanochannels (diagonal≈2.2â nm) in which inclusion molecules are located. The guest-loaded framework 1@guest displays complete thermal spin-crossover (SCO) behavior with the characteristic temperature T1/2 dependent on the guest molecule, whereas the guest-free species 1 is paramagnetic whatever the temperature. For the benzene-guest derivatives, the characteristic SCO temperature T1/2 decreases as the Hammet σp parameter increases. In general, the 1@guest series shows large entropy variations associated with the SCO and conformational changes of the interpenetrated grids that leads to a crystallographic-phase transition when the guest is benzonitrile or acetonitrile/H2 O.
ABSTRACT
The compound [Ni(3)(tppz)(2)(NCS)(2)(H(2)O)(4)](NO(3))(4).4H(2)O [tppz = 2,3,5,6-tetrakis(2-pyridyl)pyrazine and NCS = thiocyanate ligand] consists of trimeric units, where the three Ni(II) cations are linked by two bis-tridentate tppz ligands. This compound crystallizes in the monoclinic space group C2/c, with Z = 4, a = 25.1116(12) A, b = 10.8127(5) A, c = 25.2294(13) A, and beta = 116.856(5) degrees . The crystal structure is in good agreement with the antiferromagnetic interactions because of unidirectional coupling through the tppz ligands.
